Background: Scientific studies have shown female soccer athletes to be 3 times more likely to injure their anterior cruciate ligament (ACL) than their male counterparts and the majority of these injuries are from a non-contact mechanism. The biomechanical factors of this phenomenon have been extensively studied in a laboratory-based setting, but there has been little progress in reducing the incidence of ACL injury in young female athletes. It is plausible, therefore, to suggest that the biomechanical improvements noted in a laboratory-based setting do not directly translate to a field-based setting. Preventive neuromuscular training programs are typically field-based and have been shown to be an effective intervention for reducing ACL injury risk by improving dynamic, frontal-plane knee stability. However, these programs are time consuming and prone to compliance and implementation issues. For these reasons, researchers have attempted to identify the minimum viable training program or wearable device that can be studied in the field using video cameras to determine their influence on movement-related risk factors for ACL injury. Purpose: The aim of this study was to evaluate the effectiveness of a wearable neuromuscular device (WND) with or without the addition of a field-based, preventive neuromuscular training program on jump-landing risk assessment in young female soccer athletes. Methods: Thirty-nine female soccer players (161.0 +/- 6.6 cm; 49.4 kg +/- 5.9; 13.3 +/- 0.5 y) from two different teams in a local soccer club volunteered to participate in this study. Team 1 (n = 25) performed a 6-week, field-based NMT program while wearing a WND. The NMT was instructed by a trained exercise specialist. The NMT program was divided into three, two-week blocks of progressively increasing levels of exercise complexity and intensity focused on improving the strength and activation behavior of the trunk, hip and thigh muscles. Field-based movement testing was performed in the first week before training began (pre-test) and in the seventh week upon completion of the NMT program (post-test). During testing video cameras recorded a jump-landing task in the frontal and sagittal planes. The Landing Error Scoring System (LESS) and a novel version of the LESS (LESS-RMC) was used to asses movement quality related to ACL injury risk. Team 2 (n=14) wore the WND for an equal amount of athletic exposures over 7 weeks but did not perform the NMT program. Four different raters were recruited to visually score all jump landing trials using the two different rating protocols during the pre-test and post-test. For each visual assessment (LESS & LESS-RMC) a repeated measures ANOVA was conducted to explore within group (test) and between group (team) differences. Results: Repeated measure ANOVA results for the LESS score scale indicated a significant within factor difference in pretest and post test scores F(7.398, 27.533) = 8.598, P < 0.05. Pretest scores for team 1 (6.18 +/- 1.68) and team 2 (6.95 +/- 0.94) both saw a significant reduction in ACL risk scores to 5.44 +/- 1.70 and 6.31 +/- 1.75, respectively. ANOVA results for the LESS-RMC scale also indicated a significant within factor difference in pretest and posttests F(6.756, 35.624) = 6.069, p < 0.05. Pretest scores for Team 1 (6.02 +/- 1.99) and Team 2 (6.49 +/- 1.33) both saw a significant reduction in ACL risk scores to 5.10 +/- 1.77 and 6.09 +/- 1.50, respectively. ANOVA results revealed no significant differences between team scores for the LESS (F(0.031,27.533) = 0.036, p > 0.05) or LESS-RMC (F(1.053,35.624) = .946, p > 0.05) scales. Conclusion: The results reveal that the NMT program utilized in this study had no statistically significant additive effect on the visual risk assessment scores for Team 1 compared to Team 2, who had no NMT intervention and only wore the WND. Collectively, these results suggest that simply wearing a WND during 6 weeks of practice may be a less evasive and cheaper alternative to a NMT program.
Muscle Activation During ACL Injury Risk Movements in Young Female Athletes: A Narrative Review